The capture of radiation-detection views of a given object using penetrating energy (such as X-rays or the like) is well known in the art. Such radiation-detection views often comprise images having areas that are relatively darker or lighter (or which otherwise contrast with respect to one another) as a function of the density, path length, and/or composition of the constituent materials that comprise the object being imaged. This, in turn, can serve to provide views of objects that are otherwise occluded from visual inspection.
The use of radiation-detection views finds myriad applications. In at least some application settings, however, merely ascertaining the presence or shape of an occluded object may be insufficient to address all attendant needs. In a security application setting, for example, objects that pose a serious security concern may share a same shape with other completely innocuous objects. In cases where the densities of such objects are similar, it can become impossible to discern from such data which constitutes a threat and which does not. A similar problem can occur for some modalities when the density and path length product for two objects is substantially the same notwithstanding that they are formed of different materials. As a simple illustration in this regard, a three inch thick piece of steel may look substantially the same using radiography as a 1.75 inch thick piece of lead notwithstanding that these two materials have considerably different densities.
There are prior art suggestions that different materials can be discriminated from one another by using two different basis functions (i.e., functions that serve to represent (exactly or approximately) given members of a class as a weighted sum thereof). A specific example in those regards suggests using information regarding soft-tissue and bone space as a two-dimensional approach to represent other materials as well. While useful to help discriminate some materials as opposed to a few selective others, the scale of the problem space can overwhelm such an approach. Presuming, for example, that there are 95 (or so) elements of potential interest, one should presumably employ 95 (or so) corresponding basis functions to have a genuinely robust mechanism to unambiguously identify all 95 (or so) elements. Accommodating such a need, however, can require an undue amount of processing time and/or processing resources.
Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. Certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. The terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.